From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: balbir@linux.vnet.ibm.com
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>,
Li Zefan <lizf@cn.fujitsu.com>,
linux-kernel@vger.kernel.org,
Dhaval Giani <dhaval@linux.vnet.ibm.com>,
Paul Menage <menage@google.com>, Ingo Molnar <mingo@elte.hu>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH -tip] cpuacct: Make cpuacct hierarchy walk in cpuacct_charge() safe when rcupreempt is used.
Date: Tue, 17 Mar 2009 15:04:46 +0100 [thread overview]
Message-ID: <1237298686.7867.17.camel@twins> (raw)
In-Reply-To: <20090317135938.GV16897@balbir.in.ibm.com>
On Tue, 2009-03-17 at 19:29 +0530, Balbir Singh wrote:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> [2009-03-17 14:26:01]:
>
> > On Tue, 2009-03-17 at 18:42 +0530, Balbir Singh wrote:
> >
> > > I'd like to get the patches in -tip and see the results, I would
> > > recommend using percpu_counter_sum() while reading the data as an
> > > enhancement to this patch. If user space does not overwhelm with a lot
> > > of reads, sum would work out better.
> >
> > You trust userspace? I'd rather not.
> >
>
> Fair enough.. A badly written application monitor can frequently read
> this data and cause horrible performance issues. On the other hand
> large number of CPUs can make the lag even worse. Is it time yet for
> percpu_counter batch numbers? I've tested this patch and the results
> were not badly off the mark.
I'd rather err on the side of caution here, you might get some crazy
folks depending on it and then expecting us to maintain it.
next prev parent reply other threads:[~2009-03-17 14:05 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-17 6:17 [PATCH -tip] cpuacct: Make cpuacct hierarchy walk in cpuacct_charge() safe when rcupreempt is used Bharata B Rao
2009-03-17 6:28 ` Li Zefan
2009-03-17 7:36 ` Bharata B Rao
2009-03-17 13:12 ` Balbir Singh
2009-03-17 13:26 ` Peter Zijlstra
2009-03-17 13:59 ` Balbir Singh
2009-03-17 14:04 ` Peter Zijlstra [this message]
2009-03-18 3:25 ` Bharata B Rao
2009-03-18 3:54 ` KAMEZAWA Hiroyuki
2009-03-18 4:48 ` Bharata B Rao
2009-03-18 7:08 ` KAMEZAWA Hiroyuki
2009-03-18 8:05 ` Bharata B Rao
2009-03-17 23:59 ` KAMEZAWA Hiroyuki
2009-03-18 3:18 ` Bharata B Rao
2009-03-18 9:36 ` Balbir Singh
2009-03-19 9:20 ` Peter Zijlstra
2009-03-19 9:43 ` Bharata B Rao
2009-03-17 12:40 ` Balbir Singh
2009-03-18 1:40 ` Li Zefan
2009-03-18 2:59 ` Balbir Singh
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1237298686.7867.17.camel@twins \
--to=a.p.zijlstra@chello.nl \
--cc=balbir@linux.vnet.ibm.com \
--cc=bharata@linux.vnet.ibm.com \
--cc=dhaval@linux.vnet.ibm.com \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=lizf@cn.fujitsu.com \
--cc=menage@google.com \
--cc=mingo@elte.hu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox